AutomationDirect DL105, User Manual

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Drum
Instruction
Programming
6--6
Drum Instruction Programming
DL105 PLC User Manual, 3rd Edition
Step transitions do not require both the event and the timer criteria programmed for
each step. You have the option of programming just one of the two, and even mixing
transition types among all the steps of the drum. For example, you might want Step 1
to transition on an event, Step 2 to transition on time only, and Step 3 to transition on
both time and an event. Furthermore, you may elect to use only part of the 16 steps,
and only part of the 16 outputs.
Is Step event
true?
F
f f f F f F f f f f F F f f f
Step 1
Outputs:
f f f
F f f f f F F f F f f F F
Step 2
Outputs:
No
Yes
Use next transition criteria
Each drum instruction uses the resources of four counters in the CPU. When
programming the drum instruction, you select the first counter number. The drum
also uses the next three counters automatically. The counter bit associated with the
first counter turns on when the drum has completed its cycle, going off when the
drum is reset. These counter values and the counter bit precisely indicate the
progress of the drum instruction, and can be monitored by your ladder program.
Suppose we program a timer drum to have
8 steps, and we select CT10 for the
counter number (remember, counter
numbering is in octal). Counter usage is
shown to the right. The right column holds
typical values, interpreted below.
CT10
Counts in step V1010 1528
CT11
Timer Value V1011 0200
CT12
Preset Step V1012 0001
CT13
Current Step V1013 0004
Counter Assignments
CT10 shows that we are at the 1528th count in the current step, which is step 4
(shown in CT13). If we have programmed step 4 to have 3000 counts, then the step
is just over half completed. CT11 is the count timer, shown in units of 0.01 seconds.
So, each least-significant-digit change represents 0.01 seconds. The value of 200
means that we have been in the current count (1528) for 2 seconds (0.01 x 100).
Finally, CT12 holds the preset step value which was programmed into the drum
instruction. When the drum’s Reset input is active, it presets to step 1 in this case.
The value of CT12 changes only if the ladder program writes to it, or the drum
instruction is edited and the program is restarted. Counter bit CT10 turns on when
the drum cycle is complete, and turns off when the drum is reset.
Event-Only
Transitions
Counter
Assignments